The X Effect is a reality show that began airing on MTV in March 2007. The concept is that pair of exes – an ex-boyfriend and ex-girlfriend (though at least one episode with gay couples has been produced) – spend a weekend at a resort hotel, during which time they are given various romantic activities while the others ("O's") covertly watch them. At the end of the weekend, the exes must choose between their old and new partners

Source: Wikipedia.org